Portable telephone extension



Nov. 15, 1949 J. D. WIENER 2,488,153

PORTABLE TELEPHONE EXTENSION- Filed March 4, 1947 2 Sheets-Sheet 1 EXCHHNGE EXCHHNGE IN VEN TOR.

F7 TTOENEV Patented Nov. 15, 1949 UNITED STATES TENT OFFICE 2 Claims.

This invention relates generally to a portable telephone extension apparatus, the portable portion of which is of small, light construction. More specifically, this invention relates to a portable telephone extension apparatus comprising a phone unit, which may or may not be stationary, adapted to be positioned adjacent a conventional telephone, and a portable field unit of very small, light construction which may be carried about very readily, each unit including a radio transmitter and a radio receiver, the phone unit transmitter and the field unit receiver being tuned to the same carrier frequency and the field unit transmitter and the phone unit receiver both being tuned to the same carrier frequency which is dififerent from the first-mentioned carrier frequency of the phone unit transmitter and field unit receiver.

The apparatus of this invention has numerous advantages. At the present time telephone extensions being connected by leads to the telephone lines in parallel to the primary phone, are fixed in the location where they are installed, with, of course, a radius of freedom equal to the free length of the connecting leads about the point of connection thereof to the telephone lines at a suitable terminal box or the like. Thus in large homes, estates, golf courses, industrial plants, parks, farms, oifices, and the like, it is generally necessary to have a number of telephone extensions if one is to be within hearing distance of the telephone ringer so that one may know when there is an incoming call. This is exceedingly inconvenient, since one may not move about freely over a large area and must remain within hearing distance of the phone or the extensions connected thereto. It is also a very wasteful and expensive arrangement, since the telephone receivers, transmitters and associated circuits must be duplicated at each telephone extension.

Furthermore, if one is out of doors on a large estate, golf course, park, or farm, or the like, even if numerous telephone extensions are provided, one will probably be out of hearing range of the ringers associated therewith; Also, for example, doctors, clinical laboratory technicians, and various other people employed or engaged in vitally essential activities may desire to be available or on call at all times. At the present time, such individuals find it necessary when going to a golf course, or the like, to leave word with an attendant (who will receive incoming phone calls) so that if an incoming call comes to the doctor, for example, the attendant may 55 I then go out on the golf course, locate him and bring him to the phone. This is a very inconvenient and time-consuming procedure. Through the use of the apparatus of the present inven tion, the doctor could receive his incoming calls while out on the golf course.

Furthermore, since the field unit of the apparatus of the present invention is portable, the apparatus of the present invention actually comprises an infinite number of telephone extensions which have numerous advantages over any existing telephone extension systems. An important oiTicial or executive of an industrial concern, for example, at the present time when moving about the plant must generally be located by the use of a public address system. With the apparatus of the present invention, he may be called directly, no matter where he is'in the plant.

While the apparatus of this invention is intended primarily as a telephone extension adapted to function within a relatively limited range of the primary telephone associated therewith, it may, if desired, be utilized as a long distance telephone extension by arranging the transmitting range of the phone unit transmitter and the field unit transmitter to operate at the required.

distances, or it may be limited to any desired local range of action.

Generally speaking, the apparatus comprises a phone unit and a portable field unit. The phone unit includes a radio transmitter and a radio receiver, and the field unit includes a radio transmitter and radio receiver, the field unit receiver being adapted to receive the output of the phone unit transmitter and the phone unit receiver being adapted to receive the output of the field unit transmitter. The phone unit radio receiver is provided with selectively connectible audio output circuit means. Means are operatively associated with the phone unit radio receiver and responsive to carrier frequency received thereby from the portable unit radio transmitter for selectively, operatively connecting said phone radio receiver and audio output circuit means to the telephone lines in a manner simulating the connection of a telephone microphone thereto when the telephone microphone is operatively connected to the exchange.

With the above points in mind, it is an object of this invention to provide a portable telephone extension system including a phone unit and a portable field unit of small, light construction adapted to be carried about at will.

It is a further object of this invention to provide a portable telephone extension system including a phone unit and a small, light, portable field unit, both the phone unit and the field unit comprising two-way radio sets.

It is a further object of this invention to provide a portable telephone extension system in-v cluding a phone unit and a small, light, portable field unit wherein actuation of the field unit transmitter results in action in the telephone lines simulating the closing of a telephone microphone circuit.

It is a further object of this invention in a portable telephone extension system of the character described to provide a new and; novel meansand method of translating received telephone voice currents into audio input to the phone unit radio transmitter, and a new and novel means and method for translating audio output from the phone unit radio receiver into voice current input in the telephone lines.

Other and allied objects will become apparent to those skilled in the art from a careful examination and study of the illustrations, specification, and appended claims. To facilitate understanding, reference will be had to the following drawings, in which:

Fig. 1 is a diagrammatic, electrical, schematic drawing of one form of conventional dial telephone set which will be used in explaining the principles on which this invention is based.

Fig. 2 is a simplified, diagrammatic, schematic, electrical drawing, taken fromFig. 1, deleting certain elements therefrom to facilitate understanding of the invention.

Fig. 3 is a diagrammatic, electrical schematic drawing illustrating one embodiment of the phone unit and its operative connections to the telephone line.

Fig. 4 is a perspective view of one embodiment of the portable field unit.

It should be noted that the figures relating to the exemplary form of this invention show a portable telephone extension system adapted to receive incoming telephone calls at the field unit and which is not adapted to place outgoing calls from the field unit. However, the system may be very simply modified, as explained hereinafter, so as to be capable of placing outgoing calls from the field unit. It is not as necessary to be able to place outgoing calls from the field unit as itis to be able to receive incoming calls, since generally when one wishes to place an outgoing call he can go to the telephone. However, one does not know when there are incoming calls unless he is adjacent a telephone or the field unit of the present invention. Thus the primary purpose of the present invention is to provide a portable telephone extension answering apparatus and it is so illustrated herein, although not limited to this form.

More specifically, referring to Fig. 1, a conventional, antiside tone, common battery, dial telephone set is shown. The operation of this circuit will not be described in detail since it is well known in the art. However, certain points thereof will be explained so as to facilitate understanding ofv the present invention.

It should be noted that the. dial indicated gen.- erally at l is connected across the two telephone lines 2 and 3 and is adapted to make and break a closed circuit to the telephone exchange includingsaid lines 2 and 3. ihis is for the purpose of causing relay and switch mechanism in the central exchange to select the proper lines' to the party being called. Said dial I also includes means for shunting the telephone. microphone 0r transmitter and receiver during dialing in a manner well known in the art. The dial 1 and associated apparatus just described is not pertinent to the discussion immediately following and is deleted in Fig. 2, as is the ringer circuit, indicated generally at 4, which is connected across the telephone lines 2 and 3.

Referring to Fig. 2 (which has been arrived at by modifying Fig. 1 as hereinbefore described), it should be noted that at all times there is a D.-C. voltage applied in series with the lines 2 and 3 which, however, cannot cause D.-C. current to flow through the induction coil indicated generally at 5 into the connecting lead 6 because of a condenser I placed in series with the connecting lead 6. Said D.-C. Voltage cannot cause a D.-C. current to how through the portion 8 of the in-- duction coil indicated generally at 5 into the telephone transmitter or microphone 9 when the telephone is on the hook and the switch I0 is open. However, as soon as the telephone is taken off the cradle, or the receiver is lifted from the hook in the older type set, the switch it) closes and the herein-before mentioned D.-C. voltage causes a D.-C. current to flow through the portion 8 of the induction coil 5, through the telephone transmitter or microphone 9, and the switch 10. This D..-C. current flowing in the lines 2 and 3 actuates suitable relays. in the telephone exchange for opera'tively connecting the. two parties at opposite ends of'the telephone connection and is necessary to make such connection. In parallel with the portion ll of the induction coil 5 is a switch l2 and the telephone receiver l3 in series therewith. The switch I2 is adapted tobe open when the receiver is on the hook and, is adapted to be closed when the receiver is lifted off the hook, thus connecting the receiver l3 across said portion ll of the induction coil 5.

It should be noted that the above discussion has made it clear that the one essential operation when receiving an incoming telephone call, is the closing of the switch It for allowing a D.-C. current flow through the leads 2 and 3 to the telephone exchange to take place.

Keeping the above points in mind and referring to Fig. 3, it can be seen that an audio transformer secondary coil M has been substituted for the microphone 9 of Fig. 2, a relay-controlled switch 15 has been substituted for the switch I ll of Fig. 2, and a level control indicated generall at it has been substituted for the telephone receiver 53 of Fig. 2. The switch l2 of Fig. 2 has been effectively permanently closed or deleted entirely in Fig. 3. Otherwise, the telephone components and circuit contained in the dash line box indicated generally at H, are connected in the same manner shown in Fig. 2, except that the leads 2' and 3 are connected in parallel to the leads 2 and 3 coming from the telephone set of Fig. 1 at a suitable terminal block it.

The operation of the telephone component circuit. shown in Fig. 3 is similar to that shown in Figs. 1 and 2', the level control l6 being variable resistances or impedances so arranged as to match the impedance of the telephone receiver l3 of Fig. 2 which it replaces, and suitable potentiometer means being including in the level control l-6 for picking ofi output therefrom and feeding same at terminals I9 and 20 into a preamplifier, indicated generally at 2|, preferably of the electronic type. The purpose of the preamplifier 2| is to step up the received telephone voice current .input thereto, which may be of too low an amplitude to properly modulate the radio frequency carrier. The preamplifier 2| is shown in diagrammatic form only since it is well known in the art and may be of any desired form.

The output of the preamplifier 2| is connected by leads 22 and 23 to the phone unit radio frequency transmitter, indicated generally at 24, which may be of any of the types well known in the art and which is shown diagrammatically only. The phone unit radio transmitter 24 transmits a radio frequency carrier wave modulated in accordance with the received telephone voice currents. A field unit radio receiver, which is adapted to be contained in the region indicated at 25 of the portable field unit 26, shown in Fig. 4, is tuned to receive the transmitted audio frequency modulated radio frequency wave from the phone unit 24.

It should be noted that when an incoming pulsating D.-C. or alternating current is received, it is adapted to actuate the ringer at the telephone set. Said pulsating D.-C. or alternating current potential feeds a corresponding input to 'the preamplifier 2| and correspondingly modulates the radio'frequency output of the phone unit radio transmitter 24. Thus the portable field unit radio receiver receives a ringing or buzzing signal corresponding to the ringing at the actual phone. This notifies the person at the portable field unit that there is an incoming call. He then manually actuates the switch 21 which operatively connects the portable field unit radio transmitter which is adapted to be contained within the portable field unit 23 in the region indicated generally at 28. The phone unit radio receiver, indicated generally at 29, which is tuned so as to receive the output of the portable field uni-t radio transmitter receives the carrier wave from said field unit transmitter subsequent to actuation of the control switch 2'! thereof.

Refering to Fig. 3, the carrier wave received by the phone unit radio receiver 29 causes a voltage negative with respect to ground to be fed to the grids of certain of the tubes therein for reducing the output thereof. This is well known in the art and is known as automatic volume control and acts to reduce the output when the carrier frequency alone is received. The radio receiver 29 and automatic volume control are shown diagrammatically only since they are well known in the art.

The automatic volume control circuit mentioned is adapted to be connected to terminal 30 of a vacuum tube relay circuit, indicated generally at 3|, the grid 32 of which is normally negatively biased with respect to the cathode 33 thereof by means of a source of electric potential 34. The automatic volume control voltage, which is negative with respect to ground, is fed through a resistor 35 to ground at 36 which is connected to the grid 32 of the vacuum tube relay 3|. Thus the greater the AVG voltage, the more positive (or less negative) the grid 32 is with respect to the cathode 33. Thus when a carrier wave is received by the phone unit radio receiver 29 from the field unit radio transmitter and the AVG voltage from the phone unit radio receiver 29 is fed to the vacuum tube relay 3|, the plate current thereof increases, thus energizing the relay coil 31 and closing the switch l5 and holding same closed as long as the carrier wave from the field unit radio transmitter is being received by the phone unit radio receiver 29.

This closing of the switch l5 simulates the closing of the switch l0 shown in Fig. 2 and allows a D.-C. currentto flow throughthe lines 2' and 3' tothe terminal block l8 and into the lines 2 and 3 to the telephone exchange, thus closing a connection to the party calling. This makes it possible for the person at the field unit to speak into the acousto-electric transducer or microphone 38 associated with the field unit radio trans mitter, thus modulating the radio frequency carrier wave output of said transmitter which will be received and be demodulated by the phone unit radio receiver 29, the audio output of which is fed into terminals 39 and 40 which are connected to the primary coil 4| of an audio transformer, indicated generally at 42, the secondary coil M of said transformer being adapted to simulate the microphone 9 shown in Fig. 2 and to feed the audio signal into the telephone system in a manner similar to the microphone 9 input to the telephone system, as shown in Figs. 1 and 2.

Thus the audio transformer 42, shown in Fig. Bsimulates the telephone transmitter or microphone 9 shown in Figs. 1 and 2; and the control tube 3|, relay coil 31 energized thereby, and switch 5 actuated thereby simulate the switch H] of Figs. 1 and 2, which is normallyactuated by lifting the receiver of a phone; and the level control l6, shown in Fig. 3, simulates the telephone receiver |3 shown in Fig. 2. Thus a system is provided which functions in a manner simulating the nor-' mal operating conditions of a telephone set.

It should be noted that the various elements used herein should be impedance matched with the balance of the circuit and/or the elements they replace if the system is to remain unaltered.

The incoming telephone voice currents received from the party calling are fed through the level control l6, preamplifier 2|, and phone unit radio transmitter 24 to the field unit radio receiver and electro-acoustically transduced in the electro-acoustic transducer or loud speaker 43 so that the party at the field unit may hear the voice of the calling party. Thus a complete two-way telephone conversation ma be initiated and maintained.

The field unit 26 may be so modified as to make it possible to place an outgoing call from the field unit. This may be done by placing a dial thereon adapted to make and break an electric current which modulates the carrier frequency output of the field unit transmitter. This modulated signal will be received by the phone unit radio receiver 29 and demodulated, feeding a correspondingly interrupted AVC voltage to the vacuum tube relay 3| which will correspondingly vary Or intermittently interrupt the plate current thereof and intermittently energize the relay 3! in the plate circuit thereof. This will cause an intermittent closing and opening, or making and breaking of the switch l5, thus intermittently making and breaking the D.-C. current through leads 2' and 3 to the corresponding telephone lines 2 and 3 to the telephone exchange. This will actuate the selector mechanism in the telephone exchange for selecting the telephone set of the party to which the call is to be placed, in a, manner simulating the action of the customary dial telephone. If desired, means may be provided on the field unit 26 and functioning in a manner similar to that just described, adapted to cause the proper number of interruptions in the series circuit 2-3' for connecting the apparatus to the telephone operator at the exchange, who may then complete the call to the desired telephone set at the other end. The apparatus just described requires that the. relays in the vacuum tube relay 3| be of a rapid-acting type. Various other means may al'so be prorvidedfon interrupting: the series circuit- 2.'--3 for actuating the selector mechanism apparatusin the telephone exchange so as to selectthe desired telephone set at the other end, the'example described'being illustrative only.

It should be noted that whenever the apparatus is to be utilized and the portable field unit is to be carried away from the. telephone unit, the phone unit transmitter 24 may be manually switched on and the field unit radio receiver may also be manually switched on by means of switch 44. Thus the apparatus will. beyin' condition to operate as hereinbefore described; that is, the incoming ringing signal will be picked up and transmitted by the phone unit transmitter 24 and received by the portable field unit receiver and electro-acoustically transduced by loudspeaker 43 associated therewith so that the party carrying the field unit will know that there is an incomingcall. He may then manually actuate a switch 21 which turns on the field unit transmitter, the carrier frequency of which, as hereinbefore described, will be picked up by the phone unit radio receiver 29, the AVG voltage. of which, through vacuum tube voltmeter 3!, will energize relay 3:1

and close the switch l5 for the duration of the time the field unit transmitter is on, and the phone unit radioreceiver, 29 demodulates the carrier frequency transmitted from the field unit radio transmitter and feeds the audio output through audio transformer 42 into the series circuit 23' in a manner simulating the action of the telephone microphone. 9 of Fig. 2. This is effectively the same as lifting a telephone receiver from the hook and answering the phone, as hereinbefore explained. Thus the two-wa contact is established.

However, the apparatus may function in a somewhat different manner. For example, the phone unit radio transmitter 24 may not normally be turned on when it is desired to place the unit in operative condition. Means associated with the telephone components shown in Fig. 3' and responsive to ringing current received when there is an incoming call may be utilized to turn on the phone unit radio transmitter. 24 which will then transmit the sound of the ringing to the field unit radio receiver as hereinbefore described. If desired, such ringing current responsive means may also turnon the phone unit radio receiver 29. Such means are'well known in the art and are not shown.

Furthermore, the field unit radio receiver may not normally be turned on', but means associated therewith responsive to the radio carrier wave emitted by the phone unit transmitter 24 may be adapted to turn on the field unit receiver, thus placing it in condition for operation, as hereinbefore described. The phone unit radio receiver 29 may be normally turned ofi and adapted to be turned on by means. associated therewith responsive to the carrier frequency transmitted from the field unit radio transmitter. If desired, the field unit radio receiver may be turned off when the field unit radio transmitter is turned on for transmitting a message to the party at the other end of the line. If such is the case, the switch l5 or relay 3'! should be of a type adapted to be maintained closedv during the entire telephone conversation, said switch being adapted to open in response to varying the carrier transmitted from the field unit radio transmitter in some predetermined manner at the end of. the telephone. conversation.

a The vacuum tube relay 3:1. associated with: thephone-unit radio receiver 29 and adapted to. close. the-switch l5 in response. to: receipt of a. carrier. wave transmitted by' the field unit radio trans.- mitter may be varied in many possible ways well known in the art or. in. entirely different forms: of apparatus utilized therefor in respect to the receipt of said field unit carrier wave.

The apparatus herein described is adapted for use with telephone circuits of various kinds and is not limited to the specific kind of antiside tone= circuits shown herein; The preamplifier 2| may: be dispensed with in some forms of this invention, if desired; The apparatus of this invention may be modified andadapted for use in dial or manual telephone systems of the common battery or magneto type. It is adapted for use-in any anch all types of telephone head set operations. The apparatus of thisinvention maybe utilized? in intercommunicationsystems operating over'wires rather than in the usual telephone apparatus.. The apparatus of this invention may be provided: with holding keys for holding one line of com:-- munication open while-talking over a second line of communication.

Suitable antennae may be provided for the transmitters and receivers in a manner well: known in the art and. not shown herein.

The examples described and illustrated. herein are exemplary only and are notintended to limit: the scope of this invention, which is to be inter preted in the light of the appended claims only;

' I claim:

1. In combination with a telephone substation including a plurality of induction coils in.

series and a condenser across the telephone lines:

a level control means connected across an inter:- mediate induction coil of said series in lieu of a telephone receiver; a preamplifier fed by saidlevel control means; an audio transformer having a primary winding and a secondary winding; a relay-actuated switch; a circuit across said: telephone lines including one of said induction coils, the secondary winding of the audio trans-- former and the relay-actuated switch; a phoneunit. radio transmitter operably connected to the preamplifier; and a phone unit radio receiver of the automatic volume control type operably connected to the primary winding of the audio transformer and arranged to operate said relay-com. trolled switch by automatic volume control"- voltage generated in said receiver.

2. In combination with a telephone sub-station: including a plurality of induction coils in series and a condenser across the telephone lines: a level control means connected across an intermediate induction coil of said series in lieu of a telephone receiver; a preamplifier fed by said level control means; an audio transformer having: aprimary winding and a secondary winding; a relay-actuated switch; a circuit across said telephone lines including one of said induction coils, the secondary winding of the audio transformer and the relay-actuated switch; a phone unit radio transmitter operably connected to the pro-- amplifier; a phone unit radio receiver of the automatic volume control type operably con nected to the primary winding of the audio transformer and arranged to operate said relay-controlled switch by automatic volume control voltage generated in said receiver; and a portable field unit including a radio transmitter and associated input acousto-electric transducer operating on a frequency other than the frequency of the phone unit transmitter, and a radio receiver and an output electro-acoustic transducer associated therewith, said receiver being attuned to Number the frequency of the phone unit transmitter. 2,129,332 JAY D. WIENER. 2,237,457 2,248,746 REFERENCES CITED 5 2,292,222 The following references are of record in the file of this patent. 2:401:333 UNITED STATES PATENTS 2,407,417 Number Name Date 10 23541493 2,098,286 Garfield Nov. 9, 1937 10 Name Date Mastini Sept. 6, 1938 Telegen Apr. 8, 1941 Davis July 8, 1941 Haigis Aug. 4, 1942 Foster Sept. 15, 1942 Hansell Feb. 13, 1945 Bumstead June 4, 1946 Halstead. Sept. 10, 1946 Bartelink Nov. 23, 1948 

